Side Effects of Muscle Relaxants

Muscle relaxants are widely used to treat muscle pain and muscle spasms due to conditions ranging from cerebral palsy and spinal cord injuries to muscle strains. Although muscle relaxants are effective in alleviating pain and uncontrolled movements, there are potential side effects you should be aware of before taking muscle relaxants.

What Are Muscle Relaxants?

Muscle relaxants are medications generally used to relieve pain, stiffness, or uncontrolled movements caused by muscle spasms. Muscle spasms happen when a muscle or a group of muscles contract uncontrollably and cannot relax. The muscle hardens, resulting in symptoms that range from mild twitching to severe pain.

Muscle relaxants work in your brain and spinal cord or directly in your muscles to help the muscles relax.

List of Muscle Relaxants

Muscle relaxants are categorized into two categories based on how they work and what symptoms they treat most effectively. They are classified as antispasticity drugs, antispasmodic drugs, or both.

Antispasticity muscle relaxants are generally used to treat involuntary muscle movements caused by cerebral palsy, multiple sclerosis, or spinal cord and brain injuries.

Antispasmodic drugs are better for relieving muscle pain due to uncontrolled muscle contractions.

The following are muscle relaxants classified as antispasticity drugs:

• baclofen (Lioresal)
• dantrolene (Dantrium)

The following muscle relaxants are considered antispasmodic drugs:

• carisoprodol (Soma)
• chlorzoxazone (Parafon Forte)
• cyclobenzaprine (Flexeril, Amrix)
• methocarbamol (Robaxin)
• orphenadrine (Norflex)

The following medications are classified as both antispasticity and antispasmodic medications:

• diazepam (Valium)
• tizanidine (Zanaflex)

What Are the Side Effects of Muscle Relaxants?

The side effects of muscle relaxants may vary based on where they work in the body. Some work in your brain, while others work on your spinal cord or directly in the muscle.

Side Effects of Cyclobenzaprine

Cyclobenzaprine works in your brain to help relieve pain and stiffness caused by muscle injuries. Common side effects associated with cyclobenzaprine include:

• Blurred vision
• Constipation
• Difficulty urinating
• Dizziness
• Drowsiness
• Dry mouth

Cyclobenzaprine may cause an irregular heartbeat. Before taking this medication, be sure to let your doctor know if you have heart problems.

Side Effects of Tizanidine

Tizanidine works in your brain to relieve muscle spasms caused by multiple sclerosis, stroke, or brain and spinal cord injuries. Common side effects seen with tizanidine include:

• Blurred vision
• Dizziness
• Drowsiness
• Dry mouth
• Nervousness
• Upset stomach

Tizanidine may cause an irregular heartbeat, especially if you have heart problems, or if you take any the following medications:

• cimetidine (Tagamet)
• ciprofloxacin (Cipro)
• famotidine (Pepcid)
• fluvoxamine (Luvox)
• medications to regulate heart rhythm
• some birth control pills

Side Effects of Baclofen

Baclofen works in your brain to reduce involuntary movements caused by multiple sclerosis or spinal cord injuries. The most common side effects seen with baclofen include:

• Dizziness
• Insomnia (difficulty falling asleep or staying asleep)
• Tiredness
• Weakness

Abruptly stopping baclofen may cause the following side effects:

• Confusion
• Hallucinations
• Seizures
• Worsening of muscle spasms

To stop baclofen safely, your doctor may reduce your dose gradually over a few weeks.

Side Effects of Metaxalone

Metaxalone is a central nervous system (CNS) depressant used to relieve muscle pain associated with muscle injuries. Common side effects seen with metaxalone include:

• Dizziness
• Drowsiness
• Nausea
• Vomiting

The following side effects are rare but serious.

• Hemolytic anemia (a condition in which your red blood cells are destroyed faster than your body can replace them)
• Jaundice (yellowing of the skin or eyes)
• Leukopenia (low white blood cell count)

Contact your health care provider if you experience any of the following symptoms:

• Confusion
• Excessive dizziness
• Fever
• Heart palpitations
• Pale skin
• Yellow skin or eyes

You should not take metaxalone if you have severe liver or kidney problems. Your doctor may check your liver enzyme levels while you are taking metaxalone.

Side Effects of Methocarbamol

Methocarbamol works in your brain to relieve muscle spasms. Common side effects of methocarbamol include:

• Dizziness
• Drowsiness
• Lightheadedness

Methocarbamol generally causes less drowsiness than other muscle relaxants. It is a good alternative if you cannot tolerate other muscle relaxants due to excessive sleepiness.

Side Effects of Carisoprodol

Carisoprodol acts in your brain to relieve pain caused by muscle spasms. Common side effects seen with carisoprodol include:

• Dizziness
• Drowsiness
• Fast heartbeat
• Headache
• Upset stomach

Use carisoprodol cautiously, especially if you have liver or kidney problems. The side effects of carisoprodol may increase if you take the medication for a long time or if medication levels accumulate in your body.

Side Effects of Orphenadrine

Orphenadrine is related to diphenhydramine (Benadryl), and many of its side effects are similar to those seen with diphenhydramine. Common side effects of orphenadrine include:

• Confusion
• Constipation
• Difficulty urinating
• Drowsiness
• Dry mouth

Orphenadrine may also cause heart palpitations or rapid heartbeat. Talk to your doctor or pharmacist before taking orphenadrine if you have a heart condition.

Side Effects of Chlorzoxazone

Chlorzoxazone is used to relieve stiffness and pain related to muscle injuries. Common side effects of chlorzoxazone include:

• Dizziness
• Drowsiness
• Lightheadedness

On rare occasions, chlorzoxazone may cause severe liver toxicity. Immediately inform your healthcare provider if you experience symptoms such as:

• Dark urine
• Fever
• Rash
• Yellowing of the skin or eyes

Side Effects of Dantrolene

Dantrolene works directly in the muscle to slow muscle contractions. Common side effects of dantrolene include:

• Diarrhea
• Dizziness
• Drowsiness
• Muscle weakness

Dantrolene may cause liver damage if used for a long time. You should not use this medication to treat chronic pain.

How to Get the Lowest Prescription Price for Your Muscle Relaxants

Before heading to a pharmacy near you, be sure to compare prescription prices for your muscle relaxant. You can use a prescription discount card to get the lowest prescription price for your medication.

Rosanna Sutherby is a freelance medical writer who has been a practicing pharmacist in her community for close to 20 years. She obtained her Doctor of Pharmacy from Nova Southeastern University in Ft. Lauderdale, FL. She utilizes her clinical training in the pharmacy, where she helps patients manage disease states such as asthma, diabetes, heart disease, hypertension, and many others. Dr. Sutherby reviews and recommends drug regimens based on patients’ concurrent conditions and potential drug interactions.

References:

https://www.wellrx.com/health-conditions/about/health-condition/sprains-and-strains/~default/

https://my.clevelandclinic.org/health/diseases/15466-muscle-spasms

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4103716/

https://www.wellrx.com/health-conditions/about/health-condition/multiple-sclerosis/~default/

https://www.nhlbi.nih.gov/health-topics/hemolytic-anemia#:~:text=Hemolytic%20anemia%20is%20a%20blood,than%20they%20can%20be%20replaced.

https://www.mayoclinic.org/symptoms/low-white-blood-cell-count/basics/when-to-see-doctor/sym-20050615